1. Field of the Invention
The present invention relates to semiconductor processing equipment and a method of improving corrosion resistance of such components.
2. Description of the Related Art
In the field of semiconductor processing, vacuum processing chambers are generally used for etching and chemical vapor deposition (CVD) of materials on substrates by supplying an etching or deposition gas to the vacuum chamber and application of an RF field to the gas to energize the gas into a plasma state. Examples of parallel plate, transformer coupled plasma (TCP(trademark)) which is also called inductively coupled plasma (ICP), and electron-cyclotron resonance (ECR) reactors and components thereof are disclosed in commonly owned U.S. Pat. Nos. 4,340,462; 4,948,458; 5,200,232 and 5,820,723. Because of the corrosive nature of the plasma environment in such reactors and the requirement for minimizing particle and/or heavy metal contamination, it is highly desirable for the components of such equipment to exhibit high corrosion resistance.
During processing of semiconductor substrates, the substrates are typically held in place within the vacuum chamber by substrate holders such as mechanical clamps and electrostatic clamps (ESC). Examples of such clamping systems and components thereof can be found in commonly owned U.S. Pat. Nos. 5,262,029 and 5,838,529. Process gas can be supplied to the chamber in various ways such as by gas nozzles, gas rings, gas distribution plates, etc. An example of a temperature controlled gas distribution plate for an inductively coupled plasma reactor and components thereof can be found in commonly owned U.S. Pat. No. 5,863,376. In addition to the plasma chamber equipment, other equipment used in processing semiconductor substrates include transport mechanisms, gas supply systems, liners, lift mechanisms, load locks, door mechanisms, robotic arms, fasteners, and the like. The components of such equipment are subject to a variety of corrosive conditions associated with semiconductor processing. Further, in view of the high purity requirements for processing semiconductor substrates such as silicon wafers and dielectric materials such as the glass substrates used for flat panel displays, components having improved corrosion resistance are highly desirable in such environments.
Aluminum and aluminum alloys are commonly used for walls, electrodes, substrate supports, fasteners and other components of plasma reactors. In order to prevent corrosion of the such metal components, various techniques have been proposed for coating the aluminum surface with various coatings. For instance, U.S. Pat. No. 5,641,375 discloses that aluminum chamber walls have been anodized to reduce plasma erosion and wear of the walls. The ""375 patent states that eventually the anodized layer is sputtered or etched off and the chamber must be replaced. U.S. Pat. No. 5,895,586 states that a technique for forming an erosion resistant film of Al2O3, AlC, TiN, TiC, AlN or the like on aluminum material can be found in Japanese Application Laid-Open No. 62-103379.
U.S. Pat. No. 5,680,013 states that a technique for flame spraying Al2O3 on metal surfaces of an etching chamber is disclosed in U.S. Pat. No. 4,491,496. The ""013 patent states that the differences in thermal expansion coefficients between aluminum and ceramic coatings such as aluminum oxide leads to cracking of the coatings due to thermal cycling and eventual failure of the coatings in corrosive environments. In order to protect the chamber walls, U.S. Pat. Nos. 5,366,585; 5,798,016; and 5,885,356 propose liner arrangements.
For instance, the ""016 patent discloses a liner of ceramics, aluminum, steel and/or quartz with aluminum being preferred for its ease of machinability and having a coating of aluminum oxide, Sc2O3 or Y2O3, with Al2O3 being preferred for coating aluminum to provide protection of the aluminum from plasma. The ""585 patent discloses a free standing ceramic liner having a thickness of at least 0.005 inches and machined from solid alumina. The ""585 patent also mentions use of ceramic layers which are deposited without consuming the underlying aluminum can be provided by flame sprayed or plasma sprayed aluminum oxide. The ""356 patent discloses a ceramic liner of alumina and a ceramic shield of aluminum nitride for the wafer pedestal. U.S. Pat. No. 5,885,356 discloses ceramic liner materials for use in CVD chambers.
Various coatings have been proposed for metal components of semiconductor processing equipment. For instance, U.S. Pat. No. 5,879,523 discloses a sputtering chamber wherein a thermally sprayed coating of Al2O3 is applied to a metal such as stainless steel or aluminum with an optional NiAlx bond coating therebetween. U.S. Pat. Nos. 5,522,932 and 5,891,253 disclose a rhodium coating for metal components of an apparatus used for plasma processing of substrates with an optional nickel coating therebetween. U.S. Pat. No. 5,680,013 discloses non-bonded ceramic protection for metal surfaces in a plasma processing chamber, the preferred ceramic material being sintered AlN with less preferred materials including aluminum oxide, magnesium fluoride, and magnesium oxide. U.S. Pat. No. 5,904,778 discloses a SiC CVD coating on free standing SiC for use as a chamber wall, chamber roof, or collar around the wafer.
With regard to plasma reactor components such as showerhead gas distribution systems, various proposals have been made with respect to the materials of the showerheads. For instance, commonly owned U.S. Pat. No. 5,569,356 discloses a showerhead of silicon, graphite, or silicon carbide. U.S. Pat. No. 5,494,713 discloses forming an alumite film on an aluminum electrode and a silicon coating film such as silicon oxide or silicon nitride over the alumite film. The ""713 patent states that the thickness of the silicon coating film should be 10 xcexcm or less, preferably about 5 xcexcm, since the aluminum coating film, the alumite coating film and the silicon coating film have different coefficients of linear expansion and cracks are easily generated when the thickness of the silicon coating film is too thick. A thickness below 5 xcexcm, however, is stated to be unfavorable since the protection of the aluminum substrate is insufficient. U.S. Pat. No. 4,534,816 discloses an upper showerhead electrode of stainless steel, aluminum, copper or the like. U.S. Pat. No. 4,612,077 discloses a showerhead electrode of magnesium. U.S. Pat. No. 5,888,907 discloses a showerhead electrode of amorphous carbon, SiC or Al. U.S. Pat. Nos. 5,006,220 and 5,022,979 disclose a showerhead electrode either made entirely of SiC or a base of carbon coated with SiC deposited by CVD to provide a surface layer of highly pure SiC.
In view of the need for high purity and corrosion resistance for components of semiconductor processing equipment, there is a need in the art for improvements in materials and/or coatings used for such components. Moreover, with regard to the chamber materials, any materials which can increase the service life of a plasma reactor chamber and thus reduce the down time of the apparatus, would be beneficial in reducing the cost of processing the semiconductor wafers.
According to a first aspect of the invention a process for providing an erosion resistant boron nitride/yttria composite containing coating on a surface of a semiconductor processing equipment component is provided. The process includes depositing a boron nitride/yttria composite containing coating on a surface of a processing equipment component so as to form an outer erosion resistant surface. By erosion resistant surface, it is meant a surface coating that protects underlying materials from the corrosive effects of plasma chamber gases, while resisting erosion of the coating by the plasma chamber gases. The underlying surface of the process equipment component to be coated can comprise a metal, ceramic or polymer material with a preferable material being anodized aluminum.
In a preferred embodiment, one or more intermediate metal, ceramic or polymer coatings may be used between the surface of the semiconductor processing equipment and the boron nitride/yttria composite containing coating. Metal surfaces that may be coated include anodized or unanodized aluminum, stainless steel, a refractory metal such as molybdenum or other metal or alloy used in plasma chambers. Ceramic surfaces that may be coated include alumina, SiC, AlN, Si3N4, BC or other plasma compatible ceramic material. Polymeric surfaces that may be coated include fluoropolymers such as Teflon(copyright), polyimides such as Vespel(copyright), and other polymeric materials useful in a plasma chamber at temperatures up to 200xc2x0 C.
According to a second aspect of the invention, a metal component is provided. The component includes: (a) a metal surface; (b) an optional first intermediate coating on the metal surface; (c) an optional second intermediate coating on the first intermediate coating or on the metal surface; and a boron nitride/yttria composite containing coating on said component which provides a corrosion resistant outer surface. Each of the first and second intermediate coatings may be a metal or alloy thereof, ceramic, polymer or mixture or composite of materials used in plasma chamber reactors.
According to another aspect of the invention, there is provided a semiconductor processing equipment component made of a boron nitride/yttria composite containing material. The component may include any one or more coatings employed in such equipment.